Chiral [2.2]paracyclophanes—III. The preparation of unique homochiral amino-acids derived from [2.2]paracyclophane

Breaking paracyclophane: the unexpected formation of non-symmetric disubstituted nitro[2.2]metaparacyclophanes

Substituted [2.2]metaparacyclophanes are amongst the least studied of the simple cyclophanes. This is undoubtedly the result of the lengthy syntheses of these compounds. We report the simple synthesis of a rare example of a non-symmetric [2.2]metaparacyclophane. Treatment of [2.2]paracyclophane under standard nitration conditions gives a mixture of 4-nitro[2.2]paracyclophane, 4-hydroxy-5-nitro[2.2]metaparacyclophane and a cyclohexadienone cyclophane.

The synthesis of substituted amino[2.2]paracyclophanes

Amino[2.2]paracyclophanes can be prepared by direct amination of bromo[2.2]paracyclophanes or more generally by a formylation–oxime formation–oxidation–Lossen-like rearrangement sequence.

Asymmetric Diels-Alder, Michael, and aldol reactions using a planar chiral 1,3-oxazol-2(3H)-one derived from (R)-(+)-4-hydroxy-[2.2]paracyclophane

(+)-(R)-[2.2]Paracyclophane[4,5-d]-1,3-oxazol-2(3H)-one exhibiting planar chirality has been used as a chiral auxiliary in asymmetric Diels-Alder, Michael, and aldol reactions of alpha,beta-unsaturated carboxy and enolate imides, respectively. The endo-exo- and face-diastereoselectivity is good and is controlled by the spatial relationship between the prochiral center and the C9-C10 ethylene bridge of the [2.2]paracyclophane moiety. The chiral auxiliary is easily removed and quantitatively recovered.